Alphatab Does Not Accurately Reproduce GT8’s "Transpose C to D" Feature, Causing Notation Issues

[goodgame365]

I would like to report a possible bug or at least an inconsistency I observed in the file GpifParser.ts.

Currently, the relevant part of the code looks like this:
private parseTranspose(track: Track, node: XmlNode): void { let octave: number = 0; let chromatic: number = 0; for (const c of node.childElements()) { switch (c.localName) { case 'Chromatic': chromatic = GpifParser.parseIntSafe(c.innerText, 0); break; case 'Octave': octave = GpifParser.parseIntSafe(c.innerText, 0); break; } } for (const staff of track.staves) { staff.displayTranspositionPitch = octave * 12 + chromatic; } }

I would suggest directly setting chromatic = 0; instead of reading and parsing the chromatic value:
chromatic = 0;

Reason:
In my opinion, the feature in GT8 to transpose a C major part to other keys does not add much value in practical use. More importantly, after alphatab reads this setting, it does not fully replicate the display style from the GT8 software—instead, it leads to a much more confusing and less clear representation.

To ensure better compatibility and a simpler user experience, I recommend hardcoding chromatic = 0; here.

img:

gp file:
test.zip

[Danielku15]

I agree that something is not right in the area of transpose. But your solution proposal is not quite correct: Changing the tonality of the track, leads to a change of the key signature which has further impact on the placement of notes.

Can you please file a bug (following the template) that the "C played as" option in Guitar Pro is not correctly respected? We should rather add proper support for this option than hard coding something assuming "it does not add value in practical use". If it is set, it should be respected accordingly, the tab author set it on purpose.

As far I can see with fiddling in Guitar Pro the setting only influences the Key Signature of the track to be adjusted. It has some weird impact on how Guitar Pro behaves when combining custom key signatures with the transpose setting. But it should be possible to reproduce the exact Guitar Pro behaviour.

[goodgame365]

You’re right; having this setting makes sense, and it might even be essential for professionals or those with high requirements.

For instruments such as the clarinet, F horn, and Eb saxophone, transposition is especially necessary. In fact, the sheet music for these instruments is written in transposed form to make it easier for performers to read. For example, for an instrument that actually sounds in Bb, its part will be written in C, allowing the player to use the same fingering system regardless of the instrument’s actual sounding pitch.

If alphatab can implement this and restore the feature, that would naturally be the best, though it feels like a complex project and would be a major update.
Additionally, I’ve found that this setting only changes the notation display on the score. In other words, it shows the notes as if in a different key, but the actual pitches played are still the pitches of the original key. So for now, setting chromatic = 0 doesn’t affect the pitch. What I have noticed, however, is that sometimes notes in certain keys might get rendered an octave lower.